polymer thin films with nonlinear optical groups were prepared by spin-coating poly-DRI-(anthranilic acid) on glass substrates. These films were then heated to different temperatures and cooled down to obtain samples with various degrees of cross-linking. The visible absorption decreased for samples annealed at high temperatures. Strong second-harmonic signal generated from the polymer film indicated the nonlinear side chains of the polymer were aligned macroscopically through the heat treatment without external field.